A. Field of the Invention
This invention relates to a system for injecting a soft flexible conduit into a well against the pressure of the well. It also relates to a curved guide for guiding a soft flexible conduit as its direction of movement changes.
B. The Prior Art
Some oil and gas well sub-surface operations are performed with conduit that has been inserted into the well. Fluids are pumped through the conduit for treating the well.
Generally, conduits with a steel wire sheath have been used for such operations. The steel sheath protects the outer surface of the conduit. Such conduits can therefore be handled by link belt chain drive mechanisms which force the conduit into the well. However, there are numerous drawbacks to the use of a conduit with a steel wire protective sheath. Because of the steel sheath, the conduit is not flexible enough to be wound on a small (two to three foot) drum for storage. Instead it must be wound on a large (eight to ten foot) drum. The link belt chain drive mechanisms are heavy. To use such a drive mechanism, it must be positioned directly over the wellhead. Therefore, a hoisting mechanism must be employed to properly position the drive mechanism. The large heavy drum, heavy link belt drive mechanism and hoisting equipment all required to insert a steel sheathed conduit into a well, renders such an injection system cumbersome, difficult to transfer from one well to another, and expensive.
Additionally, the steel sheath for the conduit undergoes severe bending when the conduit is wound on even a large drum. The severe bending causes the steel sheath to fail. Consequently, to guard against failure during use, a steel sheathed conduit is inserted into a well only seven to ten times before being taken out of service and replaced.
The required large, heavy equipment for inserting a steel sheathed conduit into a well, and the limited use obtained from such a conduit, have encouraged the development of a system for injecting a flexible conduit, such as a hose, into a well. The use of a hose as the flexible conduit creates certain unique requirements for the injection system. Conventional hoses have been designed with one criterion, to hold internal pressure. They have not been designed to protect the outside from wear due to handling. Therefore, if a conventional hose is to be injected into a well, the injection system has to gently handle the hose while injecting it against well pressure into the well.
One injection system for a flexible hose is disclosed in U.S. Pat. No. 3,866,679 for "APPARATUS FOR INSERTING FLEXIBLE PIPE INTO WELLS", issued Feb. 18, 1975, to Tibor Laky. The disclosed system includes a drive mechanism in communication with the well. The hose passes through the drive mechanism where it is engaged and either injected into the well against the well pressure or retrieved from the well. To minimize wear and damage to the hose's exterior as it moves from the drive mechanism into the well, the drive mechanism is aligned with and above the well. From the drive mechanism, the hose moves straight into the well.
The system as disclosed in the aforementioned Laky U.S. Pat. No. 3,866,679 patent would function to inject a hose into the well. However, it has a few practical limitations. The drive mechanism, while considerably lighter than a link belt drive mechanism for a steel sheathed conduit, is still heavy. It is estimated that such a unit would weigh on the order of 1,500 pounds. The disclosed system positions this drive mechanism off of the ground above the well on top of a lubricator. To so position the drive mechanism requires hoisting equipment and/or an excessive amount of structural support members. The hoisting equipment and structural support members complicate movement and use of the system at different well head locations. The complications increase the cost per well for using the system and decrease the number of wells that may be treated by one set of apparatus.